Renewable Energy Global Innovations features: Hydrothermal Synthesis of Manganese Oxide Encapsulated Multiporous Carbon Nanofibers for Supercapacitors

Significance Statement

Hydrothermal carbonization is a newly developed technique used in generating carbon nanofibers. Despite its many advantages have certain challenges due to its undesired surface morphology and singly resultant production of microporous carbon. A better use of the hydrothermal carbonization technique in fabricating multiporous carbon nanofibers with the encapsulation of certain metal oxides is of relevance to areas where supercapacitors, in view of energy storage application is needed. Hence, various methods need to be implemented in improving the hydrothermal carbonization technique in order to achieve this feat.

Researchers led by Professor Yong Wang from Zhejiang University in China developed a new dopamine-assisted hydrothermal carbonization technique to fabricate manganese oxide encapsulated multiporous carbon nanofibers M-MCNFs from glucose. The research work is now published in peer-reviewed journal, Nano Research.

With the addition of cryptomelane nanowires, the authors were able to verify the importance of dopamine addition, as it supported the formation of carbon nanofibers. The manganese oxide encapsulated multiporous carbon nanofibers structures contained hierarchical pore structures such as macropores, mesopores and micropores.

The presence of dopamine, which was responsible for the quick formation of carbon nanofibers also aided the cryptomelane hard-templates of manganese oxide nanowires and glucose reaction. The presence of F127 aided the discovery of mesoporous structures with higher specific surface area and volume for manganese oxide encapsulated multiporous carbon nanofibers compared with the manganese oxide carbon nanofibers.

Further results also highlighted the reduction of the cryptomelane hard-template of manganese oxide to nanowires of Mn₃O₄ nanoparticles after high-temperature  annealing. The presence of Mn₃O₄ favored the capacitive performance of the manganese oxide encapsulated multiporous carbon nanofibers as the active redox sites were enhanced by the multipores which prevents the introduction of post disposition procedure.

The structural properties with large surface areas and hierarchical pores (macropores, mesopores and micropores) made the manganese oxide encapsulated multipores carbon nanofibers a far better choice for applications of supercapacitors.

From electrochemical measurements, the authors were able to show that manganese oxide encapsulated carbon nanofibers possess a favorable charge-discharge properties as well as high cycle stability and high capacity retention when tested under different electrolytes.

The method used in fabricating the manganese oxide encapsulated multiporous carbon nanofibers by the way of the authors creates an avenue for improved energy storage applications with the use of renewable source such as biomass. The strategy also pave a way to synthesize porous carbon nanofibers from biomass.

About The Author

Yong Wang studied chemical engineering at Xiang-tan University from 1998 to 2002. He received his Ph.D. degree from Zhejiang University in 2007. After a postdoctoral stay at the Department of Chemistry, Zhejiang University, he joined the Max Planck Institute for Colloids and Interfaces in Potsdam/Germany in 2009. He rejoined Zhejiang University and became a Professor for Chemistry in 2011. His research focuses on design and synthesis of novel materials for energy conversion and storage, heterogeneous catalysis and biomass conversion.

About The Author

Haiyan Wang is a Ph.D. candidate in the Advanced Materials and Catalysis Group at Zhejiang University under the direction of Prof. Yong Wang. She received her Bachelor’s degree from Henan Normal University in 2013. Her research interests are synthesis of carbon-based nanomaterials and their applications in electrochemical energy storage and conversion devices.

Journal Reference

Wang, H., Deng, J., Chen, Y., Xu, F., Wei, Z., Wang, Y. Hydrothermal Synthesis of Manganese Oxide Encapsulated Multiporous Carbon Nanofibers for Supercapacitors, Nano Research 9 (2016) 2672-2680.

Advanced Materials and Catalysis Group, ZJU-NHU United R&D Center, Center for Chemistry of High-Performance and Novel Materials, Department of Chemistry, Zhejiang University, Hangzhou, China.

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